"\'\":\:'''\ ;---:;;iV;:i:' ,:i;::i: ■;;;:;■, Ci^'^' -' '■■•''''•(' ■, ■j'-.-c^-/.y'''-'^ i^:i:|ii| i:'-'''i'";,' ':,'iy.j^^l^i[%'.''' iggf ■-■-''--; jr 'd ■' _'y ;. j^^'itr K!.:3i.;'S- '.€: U'v2.''''^»■^-'i^'^'^*'•■^^^^'^^*'ti"^:■"^ "• ; X^- ': J THE UNIVERSITY OF ILLINOIS LIBRARY NATURAL HISTORY SURVEY 5705 ILL V. 2.cop.4 'Ti, ^f... "? ? »■? J m iMwiB i^B Yr 'rr:^ ILLINOIS BIOLOGICAL MONOGRAPHS Vol. II October, 1915 No. 2 Editorial Committee Stephen Alfred Forbes William Tri lease Henry Baldwin Ward Published under the Auspices of the Graduate School by THE University of Illinois Copyright, 1915 By the University of Illinois Distributed February 25, 1916 ON THE OSTEOLOGY OF SOME OF THE LORICATI WITH FIVE PLATES JOHN EARL GUTBERLET Contributions from the Zoological Laboratory of the University of Illinois under the direction of Henry B. Ward. No. 56 TABLE OF CONTENTS PAGE Introduction 5 Ophidon elongatus The Cranium.' 5 Facial Bones 16 Scorpionichthys marmoratus The Skull 21 Facial Bones 23 Hexagrammos decagranimus The Skull 25 Facial Bones ^ 26 Summary 27 Bibliography 29 Explanation of Plates 30 Plates 31 175] OSTEOLOGY OF LORICATI — GUTBERLET INTRODUCTION The suborder Loricati is characterized by the extension of the third suborbital bone across the cheek to the preopercle. This group has a wide range of variation and Gill has divided it into several families of which the rock fishes, or Scorpaenidae, are more generalized and the sculpins, or Cottidae, are the most specialized. The family Hexagrammi- dae comes between the two extremes, being more nearly related to the Scorpaenidae than to the Cottidae. The purpose of this paper is to make a comparative study of the osteology of these forms in order to determine their relationship. Allen (1905) states that there are many points of resemblance to the Cot- tidae to be found in their osteology, visceral organs, and vascular systems, and that Ophidon is about as closely related to Scorpionichthys, a sculpin, as it is to Hexagrammos, and should be regarded as a type of a distinct family. For this study Ophidon elongatus and Hexagrammos decagrammus of the Hexagrammidae and Scorpionichthys marmoratus of the Cottidae were selected. The material was collected at Monterey Bay, California, by Mr. William F. Allen under whose direction the work was carried on at the Zoological Laboratory of the University of Illinois. OPHIDON ELONGATUS The Cranium Except for a few ridges and grooves, the entire dorsal surface of the skull (Fig. 1) is flattened. On the anterior half there is a median rectangular groove which extends from between the posterior boundaries of the orbits to the median ridge of the ethmoid. Posterior to the groove the parietals form a ridge on either side, extending laterally and poster- iorly, from the median line to the lateral edges of the epiotics. These ridges are continuations of the long rounded ridges of tlio frontals which form the sides of the rectangular grooves. The surface of the frontals, posterior to the orbits, is somewhat porous and lias striatious which pass caudad and mesad from the edge of the orbits toward the parietals The temporal fossa is formed by the pterotics, frontals, parietals and epiotics. It extends caudad from the latero-posterior edge of the 6 ILLINOIS BIOLOGICAL MONOGRAPHS [176 frontal to the caudad end of the skiill. In the anterior half it is compar- atively shallow, but throughout the posterior half it has a depth of nearly one-third that of the skull. The fossa harbors some of the muscles of the shoulder girdle. The dilatator fossae (Fig. 5-6) are pits on the dorso-lateral edges of the skull, directly above the two articu- lar facets of the hyomandibular. Anteriorly, each pit lies in the sphenotic and posteriorly in the pterotic. The pterotic forms the greater part of the roof of the pit while the most dorsal edge of the prootic forms a part of the ventral edge. Two foramina are present in the pit for the branches of the oticus vessels. The arch of the prootic Avhich forms the bridge over the foramina for the fifth and seventh nerves, the juglar vein and the external carotids is conspicuous in Opkidon. It begins at the anterior central portion of the bone and extends dorsad to the ventral edge of the anterior articular facet of the hyomandibular on the sphenotic. Vomer. — The vomer (Fig. 1) is the anterior bone of the skull and caps the cartilage from the ends of the ethmoid and the prefrontals. It possesses both dorsal and ventral processes. The dorsal and anterior one passes upward and posteriorly and articulates with the ethmoid and prefrontals. The ventral process forms a part of the ventral surface; it passes posteriorly and gradually tapers to a point in the parasphenoid. A V-shaped slit is present in the dorsal process and forms a trough-like cavity ^^^th the ventral process, alloAving the cartilaginous portion of the ethmoid to pass into it. The anterior edge is broad V-shaped in the median line and rounded from the median portion laterad forming a large expansion at each side. Two kinds of teeth are present on the vomer; an inner row of large canine-shaped ones and ail outer row of the villiform variety in which the teeth are irregularly arranged. Both kinds are slightly curved caudad and are placed in sockets. The maxilla and premaxillary both articulate just above the vomer and cover it entirely. Ethmoid. — The anterior dorsal portion of the ethmoid (Fig. 1, 6, eth) is strongly keeled, while the posterior portion is concave longi- tudinally and ends between the frontals where it tapers to a point. There is a narrow median ridge on the keeled portion extending its full length Avith a V-shaped slit in the anterior end. The ventro-lateral depression of the anterior portion forms a cavity between it and the prefrontal, these parts forming the ventral and mesial osseous walls of the nasal pit. The longitudinal groove in the concave portion is formed by a dorso-lateral expansion on either side at its anterior end. From this point the groove passes caudad and continues as the rectangu- lar groove between the ridges of the frontals. The sides of the posterior portion are eoneave from the point at which the lateral expansions ex- 177] OSTEOLOGY OF LORICATI—GUTBERLET 7 tend out from the median line. On each side of the lateral concave sur- faces there is a deep pit produced by several pores. Prefrontal. — The paired prefrontals or ectethmoids Fig. 1, 6, pfr) are lateral to the ethmoid and anterior to the frontals. Each is a lateral expansion from the ethmoid and the frontals, having a broad base-like portion and a wing-like process extending from it which forms the anterior boundary of the orbit. The anterior portion is somewhat lower than the rest and appears as a shelf at the side of the ethmoid because of a depression on its anterior dorsal surface. This depression, together with a similar depression on the latero-ventral surface of the ethmoid forms a part of the bony wall of the nasal pit. The wing-like process is narrow antero-posteriorly but broad and flattened dorso- ventrally. The end is rounded and forms a facet for articulation with the palatal and the first exorbital bone. A small ventral process on the wing meets a process from the palatine. From the base of the wing- like portion the bone flattens out antero-posteriorly as it extends ventro- mesad to its articulation with the parasphenoid. There is a foramen through the wing near its suture with the ethmoid through which the olfactory nerve and the orbito-nasal vein and artery to the nasal pit pass. Above the point where the prefrontal unites with the parasphe- noid they come in contact with each other in the median line holding between them the ventral edge of the cartilaginous orbito-sphenoid which extends dorsad and caudad forming a partial partition between the orbits. Frontal. — The paired frontals (Figs. 1, 6, fr) form the greater part of the dorsal surface of the cranium. At the anterior end of each there is a small groove produced by pores in the bone. The lateral edges of the posterior portion form the mesial boundaries of the orbits. The posterior portion broadens and forms the posterior and dorsal boundaries of the orbits. At this point the frontals are slightly rounded dorsad and the bone is somewhat porous, possessing several striations which start at the posterior boundary of the orbit and radiate caudad and mesad toward the median line to the parietal bones. The lateral edges of the posterior portion form the mesial border of the anterior part of the temporal fossa. At the lateral edge on the posterior border of the orbit the frontal unites with the sphenotic. Its lateral edge rests on the prefrontal and the mesial edge rests on the ethmoid. In the median line on the ventral surface there is a cartilaginous orbito- sphenoid bone, extending to the parasphenoid and forming a partial partition between the orbits. The ventral surface of the roof of the orbit is filled with large pores and two deep grooves which become deeper as they pass caudad into the deeper part of the frontal. The mesial edge of the inner groove forms a large flange which projects 8 ILLINOIS BIOLOGICAL MONOGRAPHS [178 ventrad along the lateral edge of the brain ease. The outer edge of this flange narrows do^vn and, as it passes ventrad, it is drawn out to a thin process; this flange and the thin process clsisp the small alisphenoid between them as in Scorpaena described by Allis. The ventral surface of the posterior portion is smooth and in connection with supra-occipital which forms a plate beneath the parietals and posterior part of the frontals forms the roof of the brain case. Post frontal. — The postfrontal (Fig. 1, pfo) is a small tube- like bone similar to the one described by Allis in Scorpaena scorpus except that it is without spines. It lies on the part of the dorsal surface of the sphenotic which is not covered by the frontal and pterotic. The tube extends from the lateral edge of the sphenotic caudo-mesad to the anterior end of the temporal fossa. Sphenotic. — The sphenotics (Figs. 1, 6, spo) are located at the lateral margins of the cranium, just posterior to the orbits and, in conjunction with the lateral expansions of the frontals they form the posterior boundary of the orbit. The dorsal surface of each is nearly flat, except for a groove formed for the postfrontal bone which lies within it. It thus forms supports for the frontal, the postfrontal, and the ptero- tic. It forms the anterior, lateral, and ventral portions of the cranium. The anterior margin borders on the orbit and the ventro-lateral edge forms a facet for the articulation with the anterior head of the hyomand- ibular. Directly dorso-anterior to the facet is a roughened surface which serves for the attachment of one of the palatal muscles. Dorso-posterior to the facet is a depression, the dilatator fossa, the posterior part of the sphenotic forming the anterior part of the depression. Between the dorsal part of the sphenotic and the frontal, beneath the postfrontal, there is a small foramen which transmits one of the branches of the otic vessels. The sphenotic also forms a part of the internal brain case; the internal surface is smooth and has two depressions, separated by a thin partition of bone which extends mesad into the brain cavity. Prootic. — The prootic (Fig. 6, pro) forms a large part of the lateral surface of the cranium. It is bounded dorsally by the sphenotic and pterotic, anteriorly by the alisphenoid and the dorso-lateral process of the parasphenoid, ventrally by the parasphenoid, and posteriorly by the basi-occipital and exoccipital. MesiaUy it articulates with the basisphenoid and the prootic of the opposite side. On the ventral sur- face it is overlapped by the lateral edges of the posterior portion of the parasphenoid. The prootics form the lateral walls of the brain case and also the roof and walls of the myodome. The brain cavity and the myodome are separated by a mesial longitudinal partition-like process which unites with a similar one from the opposite side in the median line. This partition begins at the basioccipital, which also forms the 179] OSTEOLOGY OF LORICATI—GUTBERLET 9 posterior part of the floor of the brain ease, and extends dorso-cephalad until it reaches the processes which support the T-shaped basisphenoid, leaving a small wedge-shaped slit between the basisphenoid and the partition for the opening of the pituitary body from the brain case. Near the lateral wall, just posterior to the process which supports the basisphenoid, a small foramen for the sixth nerve preforates the parti- tion. Between the prootic, alisphenoid, and the dorso-lateral process of the parasphenoid there is a large foramen through which the anterior cerebral vein, the ciliary nerve, and ciliary artery pass. On the front edge of the foramen and slightly mesad, at the base of the process sup- porting the basisphenoid, there is a second small foramen for the third nerve. On the lateral surface of the prootic is the prootic arcade, which is located slightly dorso-posterior to the foramen between the bones just described and directly ventral to the anterior articular facet for the hyomandibular on the sphenotic. This arcade partly shelters two fora- mina. The anterior and larger one is for the passage of the jugular vein, the external carotid artery, the fifth and part of the seventh nerves. The posterior one is for the hyomandibular part of the seventh nerve. There is another small foramen for the fourth nerve just anterior to the arcade. The arcade forms an arch through which the jugular vein and external carotid artery pass after they have passed through the fora- men. On the inner surface the brain case is smooth with a large broad ridge, produced by the broad groove on the external surface, extending from near the middle just behind the arcade to the posterior end of the bone (where it unites by suture with the exoccipital and the ventral most edge of the pterotic) and continuing caudad as the ridge on the exoccipital. Directly ventral to the ridge on the internal surface, there is a deep depression or groove parallel to the ridge and extending the length of it bordering on the floor of the brain case. This groove con- tinues caudad into the basioccipital where it finally forms a recess with the overhanging edge of the exoccipital. Directly beneath the arcade there is a flange-like process extending from the floor of the brain case to the dorsal edge of the bone where it unites with a similar process of the sphenotic. This flange-like process forms two recesses for parts of the anterior semicircular canal. Alisphenoid. — The alisphenoids (Fig. 6, als) are small, irregu- lar bones, ventral to the articulation of the sphenotic and frontal where they are held in place by the clasp of the ventral flange and slender ventro-mesal process of the frontal. Each also comes in contact, ventrad and caudad, with the parasphenoid and prootic. The outer surface is porous while the inner surface is smooth and forms the latero-anterior part of the brain case. A large foramen, postero-ventral to the alisphe- noid, and between it and the prootic and the dorso-lateral process of 10 ILLINOIS BIOLOGICAL MONOGRAPHS [180 the parasphenoid, allows the passage of the anterior cerebral vein, the ciliary artery, and the ciliary nerve. Allis ( '09) found a small foramen for the anterior cerebral vein perforating the alisphenoid in Scomber, Coitus, Trigla, Peristedion, Dactylopterus, and Scorpaena and states that Allen (1905) did not describe it in Ophidon. I do not find a foramen perforating the alisphenoid in Ophddon nor in ScOrpionichthys. The anterior cerebral vein, according to Allen (1905), passes through the foramen formed by the prootic, the dorso-lateral process of the parasphenoid, and the posterior edge of the alisphenoid. Parasphenoid. — The parasphenoid (Fig. 6, ps) is the longest bone of the skull and forms the ventral surface of the entire length of the cranium with the exception of the process of the vomer which passes caudad into the parasphenoid. The anterior portion is almost perfectly straight on the ventral surface while the posterior portion is slightly curved upward and the edges of the bone turn up dorso-lateraUy, the entire length of the bone. In the middle portion the edge projects upward as a long process which extends dorso-laterally to the edge of the alisphenoid. Directly posterior to the process, in the angle between it and the prootic, is a foramen through for the internal carotid artery. The bone has a cqncave longitudinal groove the entire length of the dorsal surface which, in the anterior portion, is divided by a tall parti- tion, extending from a point immediately anterior to the tall processes to the anterior end of the bone where it terminates in the ethmoid and the vomer. At the anterior end there is a V-shaped slit on the ventral edge for the postero-ventral process of the vomer. The posterior end also has a V-shaped slit extending cephalad, forming the posterior opening of the myodome. The dorsal surface of the posterior portion forms a part of the floor of the myodome, between the prootics and the two taU dorso-lateral processes of the bone itself. This portion also forms a support for the prootics and the basioccipital. Basisphenoid. — The basisphenoid (Fig. 6, hs) is a T-shaped bone forming the anterior part of the roof of the myodome, being at- tached to the processes extending mesad from the prootic, just postero- ventrad to the alisphenoid. The pedicle is curved ventro-cephalad to the parasphenoid where it is united to it by a bulb of cartilage. It is laterally flattened and the rest of the bone between the prootic processes is dorsally flattened but rounded ventrally and slightly curved cephalad at the point where the pedicle process projects. Pterotic. — The pterotics (Figs. 1, 6, pto) form the lateral edges of the dorsal surface of the skull, posterior to the sphenotics and the postfrontals, and also the lateral borders of the temporal fossa. On the dorsal edge of such there is a narrow ridge extending from the anterior end to beyond the middle from which the surface gradually slopes to 181] OSTEOLOGY OF LORICATI—GUTBERLET 11 the lateral edge of the sknll. A foramen for a lateral line canal oceors at the posterior end ; the whole surface being nune or lew performted. The lateral surface of the pterotic is bounded eephalad by tiie spl^notie and the prootic and ventrallj bv the prootie, exocdpital, and opisthotie. At the anterior end of the bone there is a depression wfaidi fmns the posterior edge of the dilatator fossa and immediately posterior and slightly dorsal to the fossa is a facet for the articulation of the posterior head of the hyomandibular. Posterior to the facet is a broad AaXUxm groove, the dorsal edge forming the edge of the groove, extending to tlie posterior end of the bone, where it narrows as does the bone itadf. Ventro-caudad to the facet are two or three, more or less developed ridges, extending from the lower edge of the facet to the ventro-poste- rior edge of the bone where it unites by suture with the opisthotie. The ventral edge of the bone curves sharply inward, thus forming a broad rounded ridge between the facet and the point where it unites with the prootic and the exoccipitaL The antero-ventral edge of the facet forms a flange-like shelf beneath which there is a slight depiesBion forming, together with a flange-like expansion of the prootie, a tooad gtoofve extending from that point antero-ventrad on to the piootie. The inner surface of the pterotic forms Hie dorso-posterior part of the lakenl wall of the brain case, there being a large cavity passing latero-eaudad fron. the main portion of the brain case, and lying ventro-mesad to the faeet of the hyomandibular. This cavity harbors a part of the external soni- circular canal. Epiotic. — The epiotics (Fig. 1, epo) form a part of the dorsal surface of the cranium. The lateral snrfaee of each forms the mnrial boundary of the temporal fossa ; its mesial edge forms the lateral border of the supra-temporal pocket. The bone is bounded laterally by the posterior process of the parietal and pterotic; ventraUy and postero- ventrally by the exoccipital and mesiaUy by the supra-oeeipitaL It forms a tall ridge extending postero-laterad as far caudad as the pterotie and the opisthotie above the exoccipital, and neariy parallel to the pterotic. The supra-scapular lies coi the dorsal surfaces at tiie eandal ends of the epiotic and pterotic, thus forming a roof at the posterior end of the temporal fossa. At the anterior end the bones are oveilai^ied by the supra-occipital and the parietals. The internal sur&ee fomH the dorso-caudal w^ of the brain case. These parts form postmociy pockets for the posterior semicircular canals, directly above and in connection with the exoccipitaL Parietal. — The parietals (Fig. 1, p) form a part of the dorsal surface of the cranium, their lateral edges forming the mesial borders of the temporal fossa. Each is somewhat irregular in shape with its broadened end cephalad and a long slender proeess, extending 12 ILLINOIS BIOLOGICAL MONOGRAPHS [182 caudad slightly dorsad and laterad on the epiotic ridge, which in this position projects over and forms a part of the roof of the temporal fossa. At the posterior end of the process there is a foramen, passing cephalad into the bone for one of the lateral line canals. The process forms a ridge and extends antero-mesad, uniting with a similar ridge from the opposite side in the median line. The dorsal surface of the ridge is porous and possesses several striations parallel with the ridge. At the anterior end the bone joins by suture with the frontal; it is supported laterally by the pterotic and mesially and ventrally by the epiotic and supra-occipital. In the suture between the parietal and supra-occipital on each side of the median line is a foramen for the ramus lateralis accessorius vessels. The inner surface of the bone lies largely on the dorsal surface of the supra-occipital, but lateral to the plate-like supra-occipital, which covers the greater part of the cranial cavity; the parietal forms a part of the dorsal surface of the cavity where it arches over the space between supra-occipital and pterotic. Opisthotic. — The opisthotic (Fig. 6, opo) is a small plate-like bone, oval in outline, lying between the pterotic and the exoccipital. The antero-dorsal edge overlaps the postero-ventral edge of the pterotic and the ventral edge overlaps the exoccipital, thus forming the latero- caudal edge of the skull. It is drawn out caudad into a rounded process which projects beyond the exoccipital and even with the pterotic. The opisthotic forms the posterior lateral wall of the temporal fossa, from the point of its union with the pterotic on the mesial surface. The posterior end of the bone has a bulb-like appearance and is united by a cartilaginous ligament to the suprascapular. Exoccipital. — The exoccipitals (Figs. 1, 6, 8, eo) are irregu- lar bones which form a part of the lateral and of the posterior surface of the cranium and of the brain case. A well defined angle, ventral to the opisthotic, separates the lateral from the candal surfaces. That part which forms the porterior portion lies directly below the epiotic and a part of it forms the base of the epiotic ridge. The dorsal edge also borders on and forms the posterior edge of the floor of the temporal fossa. That part posterior to the angle extends backward and forms a rounded head, the occipital condyle, which looks caudad and slightly ventrad, articulating with an anterior process of the first vertebra. The two condyles are dorso-laterad to the basioccipital and laterad to the foramen magnum. Ventrad to the epiotic ridge and the temporal fossa, the bone extends caudad and mesad, uniting in the median line with its fellow of the opposite side ; thus forming the roof of the medulla oblongata. It is overlapped in the median line by a ventro-posterior process of the supra-occipital. Slightly above the angle separating the posterior and lateral surfaces, there is a small depression 183] OSTEOLOGY OF LORICATI—GUTBERLET 13 or groove, dorso-cephalad to the condyle, extending upward to the pos- terior end of the temporal fossa. The lateral surface of the bone is irregular in shape and possesses a broad deep groove extending from slightly cephalad of the angle separating the lateral and posterior sur- faces to about the middle of the prootic. At the posterior end of the groove there is the foramen for the vagus nerve and slightly anterior to this, another foramen for the glossopharyngeus nerve perforates the bone in the same groove. On the posterior, dorsal surface, anterior to the condyle, are two foramina for the passage of the occipital nerves. The internal surface forms part of the posterior and part of the lateral walls of the brain case and the dorsal wall of the medulla oblongata. The ventro-mesial edge, overlapping the basioccipital, forms a lateral recess with the groove of the basioccipital on each side of the cavum sinus imparis. Dorsal to this recess, a larger cavity which lies slightly dorso-cephalad to the vagus foramen, lodges the ampulla of the pos- terior semicircular canal. The exoccipital unites cephalad with the prootic, ventrad with the basioccipital, dorsad with the opisthotic and epiotic, and mesad with its fellow from the opposite side and the supra- occipital. Supraoccipital. — The supraoccipital (Figs. 1, 8, so) forms the dorso-posterior portion of the skull, lying between the epiotics, with a process between the exoccipitals, and also beneath the parietals and the posterior part of the frontals, thus forming the roof of the brain case as well as a part of the posterior wall. Between the epiotics it has a deep groove, extending from the dorsal surface, postero-ventrad, al- most to the foramen magnum, where it ends in a process between the exoccipitals. The groove, the supra-temporal pocket, is formed by a process on either side which overlaps the epiotics. On the dorsal sur- face it has a small longitudinal crest in the median line extending cephalad from the anterior end of the groove to the point where the bone is overlapped by the parietals. The inner surface forms the roof of the brain case as it has developed into a thin plate-like bone beneath the parietals and the posterior part of the frontals. It has a smooth surface with a ridge at the posterior end extending postero-ventrad from the dorsal surface toward the foramen magnum. Beneath the point of articulation with the parietals and frontals a small flange is developed on the ventral surface near the lateral margin which extends latero-cephalad, and unites with a similar flange from the sphenotic by a cartilaginous ligament. In the base of the flange is a foramen for the ramus lateralis accessorius vessel which passes over the supra-occipital between it and the parietal. Basioccipital. — The basioccipital (Figs. 1, 6, 8, bo) forms the. ventro-posterior end of the cranium, the posterior end of the myodome, 14 ILLINOIS BIOLOGICAL MONOGRAPHS [184 and the posterior part of the floor of the brain cavity. On its dorsal surface (floor of the brain case) are two longitudinal grooves, one on each side of the median line, lying along the lateral walls of the bone and separated by a rounded ridge in the median line. These grooves are open throughout the anterior half but are covered in the posterior half by the edges of the exoccipitals which overlap into the brain cavity and with the groove form recesses on each side as it passes backwards on each side of the pit of the cavum sinus imparls, reaching almost to the conical, vertebra-like, depression on the posterior end. The cavum sinus imparis is a deep pit on the dorsal surface in the median line near the posterior end, only separated by a single thickness of bone from the conical, vertebra-like, depression. This pit lies on the surface of the median rounded ridge between the lateral grooves which form the re- cesses in connection with the overlapping mesial edges of the exoccipi- tals. As the cavum sinus imparis passes backward it gradually becomes deeper until it forms a saccular cavity at the posterior end. The ventral surface of the bone possesses a long groove the ventro-lateral edges of which almost form a circle in connection with the parasphenoid. This groove tapers gradually into a narrow tube which passes to the posterior end and opens to the exterior by a slit-like opening on the ventral sur- face. This tube forms the posterior portion of the myodome. On the lateral surface of the bone is a rounded ridge, arising at the dorso- anterior edge, where it is a continuation of a similar ridge from the prootic, and extending postero-ventrad nearly to the ventral surface of the bone. The posterior end is rounded, with a slight conical depression which forms the facet for the articulation with the first vertebra. Myodome. — The myodome is a long funnel shaped cavity, formed by the basisphenoid, the two prootics, the parasphenoid, and the basi- occipital. The funnel is triangular in outline, located between the two prootics and ventral to the basisphenoid, the pedicle of which bisects the anterior end of the cavity. It becomes narrow as it extends caudad into the basioccipital where it tapers to a tube and opens to the exterior by a slit on the ventral surface. There is an oval opening between the basisphenoid and the partition of the prootics for the pituitary body. Immediately posterior to this opening on the dorso-lateral surface of the myodome there is a pocket which extends upward toward the trigemino-facial chamber and is only separated from it by a thin parti- tion. Here the myodome is widest and narrows rapidly caudad until it forms the tube. At the median ventral edges of prootics and basi- occipital is a long slit-like opening, the hypophysial fenestra, covered by the parasphenoid, except at the posterior end where it opens to the exterior. The myodome contains the eye muscles, which are attached to the walls and roof of the cavity and pass cephalad into the orbit. 185] OSTEOLOGY OF LORICATI —GUTBERLET IS Orbit. — The orbits are formed by the prefrontals, frontals, sphe- notics, and suborbitals. They are large in Ophidon and the two are separated by the partial partition of the orbitosphenoid which is carti- laginous at its anterior portion and membranous at the posterior. At the anterior end the partition comes in contact with the prefrontals in the median line and at the posterior end it comes in contact with the dorsal surface of the basisphenoid and the pedicle unites with the mem- brane at the point of contact with the parasphenoid. Dorsal to the basisphenoid the membranous partition divides, extends laterally and unites on each side with the ventro-mesial edge of the alisphenoid and the ventral processes of the frontal, thus forming the posterior wall of the orbit and the anterior wall of the brain cavity. Directly dorsal to the basisphenoid and slightly lateral to the median line there is an opening through the membrane for the passage of the optic nerve. Above the openings for the optic nerves in the median line against the dorsal wall there is an opening for the olfactory nerves which pass cephalad and divide, one passing on either side of the partition and through the foramina in the prefrontal into the nasal sac. Brain Cavity. — The brain cavity in Ophidon is quite large and extends from the posterior end of the orbit, from which it is sepa- rated by the lateral partitions of the infraorbital membrane, to the post- erior wall of the cranium. The cavity has a series of recesses on the dorso-lateral walls for parts of the brain and on the ventral surface there is a groove like cavity, the cavum sinus imparls, beneath the foramen mag- num. On the floor of the brain case are two grooves which extend caudad along the lateral walls of the basioccipital, parallel to the cavum sinus imparls to the posterior end. The mesial edges of the exoccipitals overlap and form saccular recesses of these grooves. Above each saccular recess there is a cavity — the part of the labyrinth enclosing that portion of the posterior semicircular canal which is located in the exoccipital. Dorsal to this is a large recess in the epiotic which is for the rest of the posterior semicircular canal. Antero-lateral to this recess in the pterotic there is a large recess for the external semicircular canal, with two pits in the ventral surface for the ampulla of this canal. One of these pits is located in the prootic and the other in the pterotic. Anterior to this recess there is another for the anterior semi-circular canal. This one is divided into two parts by a flange-like partition which extends dorso- cephalad from the floor of the cavity. The anterior part of the cavity lies in the prootic and lodges the ampulla, while the posterior lies in the sphenotic and lodges the body of the canal. Directly anterior to the anterior semicircular canal there is another shallow cavity — the trige- mino-facial chamber — which lies nearly in the line with the pituitary opening between the basisphenoid and the prootics. The dorso-anterior 16 ILLINOIS BIOLOGICAL MONOGRAPHS [186 end of the brain case is located between the ventral flanges of the frontals. Facial Bones PremaxUlary. — The premaxillary (Fig 9) is a long curved bone bearing teeth. Its anterior end is thickened and bears two dorsal processes extending dorso-caudad, with a V-shaped slit between them. The anterior process is long, slender, and laterally flattened at the base and gradually becomes rounded distally until at its end, where it articu- lates with the ethmoid, it is antero-posteriorly flattened. The posterior process is broad and thick at the base and as it nears the end it makes a sharp curve and comes to a point at its anterior edge ; on its anterior mesial surface it has a deep depression into which an angular process of the maxilla passes as it articulates with that bone. It is rounded on its dorso-lateral surface except at a point slightly posterior to the middle where it has broadened and flattened into a sharp edge ; from this point it gradually tapers to a long slender point which extends on the lateral surface of the mandible. The anterior end of the bone, anterior to the processes, is rounded and thickened as it nears the median line where it unites with its fellow from the opposite side. Two kinds of teeth are present on the premaxillary, an inner row of canine-shaped teeth and from one to several irregular rows of the villiform type. Maxillary. — The maxillary is a long curved bone without teeth, having a thick articular head and a flat expanded hind end. The former has a large articular facet which appears double on account of a V between its articular surfaces. The antero-mesial of these processes curves mesad and lies inside of the dorsal process of the premaxillary with which it articulates, directly dorsal to the dorsal limb of the vomer. The antero-lateral process is drawn out into a pointed projection lateral to the process of the premaxillary with which the other process articu- lates, and upon which the anterior ends of the nasal and palatine bones rest. At the apex of the V between the articular processes, the bone is rounded mesad at the point where it fits over the process of the pre- maxillary. The ventral edge of the first suborbital rests on the dorsal surface of the maxilla for some distance back from the anterior end. The posterior flattened and broadened end rests on the lateral edge of the mandible as it passes postero-ventrally from the anterior end. Nasal. — The nasal is a small bone connecting the prefrontal, ethmoid, and the maxilla and forming the roof of the nasal pit. It is Y-shaped, with one edge of the broad end lying on a small process on the dorso-anterior edge of the prefrontal and the other on the antero- lateral process of the ethmoid. The pedicle extends cephalad and rests upon the maxilla, thus forming the roof of the nasal pit. 187] OSTEOLOGY OF LORICATI—GUTBERLET 17' Suborbitals. — The suborbital bones, three in number, lie on the lateral surface of the skull. The anterior end of the series is firmly attached to the dorsal edges of the palatine and maxillary, also articu- lated with the prefrontal at its lateral facet. At the posterior end the third bone is attached to the preopercular, thus forming a bridge from the anterior to the posterior ends across the cheek; and also the ventral boundary of the orbit. The suborbitals are plate-like bones. The ante- rior bone is broad, somewhat oval in shape, lying on the surface of the maxillary for some distance from the anterior end. Caudad it is united with the second suborbital bone. The second bone is elongate in shape and about one-half as broad as the anterior one. This bone really forms the ventral boundary of the orbit. The third bone is the longest and passes from the edge of the orbit and is extended caudad, forming the suborbital stay. It is elongate, and is slightly broadened at the posterior end. Near the anterior end of this bone is a small postorbital, forming the posterior edge of the orbit and extending to the edge of the sphenotic. In younger specimens this is merely a cartilage but in more mature forms it becomes ossified. This is a small plate-like bone lying in the dermal tissue. Palatine. — The palatine is an irregular bone composed of two portions, a broad plate and an anterior rod. The plate is posterior and is somewhat triangular with the apex pointing caudad. On the lateral surface it is smooth except for some small narrow ridges which extend postero-ventrad from the dorso-anterior end. There is a large facet on the dorsal edge for the articulation with the prefrontal and with an edge of the first suborbital. This facet has a deep pit which extends as a groove on the dorsal edge to the posterior end, and serves for the articulation of the mesapterygoid. The mesial edge of the facet is ex- tended dorsally into a tall process which becomes attached to the ventral edge of the prefrontal. The mesial surface of the palatine is roughened by porous openings and bears a deep groove bounded by the dorso- mesial and the ventro-mesial edges of the bone extending from the anterior end of the posterior portion to the posterior end of the bone. Two kinds of teeth are present on the ventral surface which are like those on the vomer and premaxillary — an inner row of large teeth of the canine variety and outer row of small villiform type, more or less irregularly arranged. The anterior rod-shaped part of the bone is somewhat curved antero-ventro-laterally from the dorsal edge of the triangular portion, directly anterior to the articular facet of the pre- frontal and the suborbital bone. This rod is somewhat flattened dorso- ventrally at the anterior end where it articulates by a ligament with the dorsal surface of the maxillary on the antero-lateral process of the head of that bone. 18 ILLINOIS BIOLOGICAL MONOGRAPHS [188 Mesapterygoid. — The mesapterygoid, the ectopterygoid of some authors, is a long, slender, curved bone which unites the palatine with the quadrate. The anterior end of the mesapterygoid lies in the groove on the dorsal edge of the palatine, from there it passes caudad for a distance, then it curves ventrally and articulates with the anterior edge of the quadrate. It is flattened laterally at the posterior and middle parts but at the anterior end it is flattened dorso-ventrally. There is a small groove on the ventral edge where it lies in a groove on the dorsal edge of the palatine. On the dorsal edge of the mesaptery- goid there is a long slender groove for a membranous bone, the en- topterygoid, which forms a part of the ventral boundary of the orbit. At the point where the bone curves ventrally there is a plate-like process on the dorsal edge which connects with the mesapterygoid and the entopterygoid. On the posterior edge the bone possesses a slight groove where it unites with the quadrate. The bone tapers to a point at its postero-ventral end. Hyomandibular. — The hyomandibular is shaped like an arrow head with the shank extending from the ventral edge. The anterior end is drawn out into a thin, pointed, plate-like process. Slightly dorso- caudad to the pointed end is a thickened part which passes ventro- caudad across the middle of the head and also across the shank, thus forming an irregular cross with the shank. At the anterior end of the bar forming the cross is a facet, the anterior head of which articulates with the facet of the sphenotic directly above the prootic arcade. On the posterior end of the cross bar there is a facet for the articulation with the opercular. The shank passes upward through the body of the bone and forms a double facet, the posterior head of which articulates with the facet of the pterotic immediately posterior to the dilatator fossa. The dorso-caudad part of the posterior head articulates with a flange-like process dorso-caudad to the facet. The long shank extends ventrally and is united to the symplectic at its ventral end by a mass of cartilage. The metapterygoid articulates with the anterior process of the hyomandibular which is a thin membrane bone filling the space between the anterior bar of the cross and the shank. Likewise the spaces between the other bars are also filled with a thin sheet of membrane bone, thus leaving slight depressions between the bars. There is a deep pit on the mesial surface at the angle between the anterior bar and the shank, which gives rise to two canals. One passes ventrally into the bone and opens on the lateral surface of the shank just anterior to the ridge which bounds the groove for the articulation of the preopercular. This canal bears the truncus hyoideo-mandibularis facialis vessel. The other cajial passes ventrad and caudad, dividing into two parts; one opens to the exterior at the dorsal edge of the groove for the articulation 189] OSTEOLOGY OF LORICATI—GUTBERLET 19 of the preopercTilar and between the opercular bar and the shank, the other opens at the hind edge of the bone, directly beneath the opercular bar. These two canals transmit branches of the nerve of the latero- sensory canal which lies in the region of the opercular. Another small foramen, in the dorsal edge of the groove for the preopercular, trans- mits a part of the hyoid nerve between the hyomandibular and the preopercular. Symplectic. — The symplectic is a small paddle-shaped bone with a broadened end and a long slender process. It articulates at its dorsal and broadened end with the shank of the hyomandibular by a long car- tilaginous ligament. The bone for the most part lies in a triangular groove on the lateral surface of the quadrate with its long process pene- trating the bone almost to its articulating facet for the mandible. Metapterygoid. — The metapterygoid is a broad plate-like bone, more or less quadrant shaped with two plate-like processes. The quad- rant-shaped part is the ventral portion of the bone with the round edge united by a cartilaginous ligament with the dorsal edge of the quadrate. Two processes extend from the dorsal edge of the quadrant. One of these is somewhat elongated and extends dorso-cephalad coming in con- tact with the anterior process of the hyomandibular. The other extends caudad from the dorso-posterior edge of the quadrant, and bears a V- shaped slit for the hyoid artery on its ventral edge. The posterior edge comes in contact with the anterior edge of the shank of the hyomandibu- lar. Two small flanges, one on either surface of the anterior process, bound a groove on the dorsal edge which extends nearly the entire length of the process. The groove is for the union with the hyo- mandibular. Quadrate. — The quadrate is a quadrant-shaped bone with the ventral point thickened and formed into a head for the articulation of the articular. The dorsal or rounded edge is broken near the posterior edge where the bone forms a deep groove on the inner surface for the articulation of the symplectic where it passes downward into the quad- rate. There is a groove on the posterior edge extending almost the length of the bone for the contact with the preopercular. The anterior edge is somewhat roughened and possesses no groove where it articulates with the mesapterygoid. On the dorsal edge the quadrate unites by a cartilaginous ligament with the ventral edge of the metapterygoid and cephalad with the entopterygoid and mesapterygoid, caudad it unites with the preopercular and the symplectic. Preopercular. — The preopercular (Fig. 4) is a long, flat, curved bone with three small barbs on its posterior side. A lateral line sensory canal runs throughout its length, opening near the edge of the ventral barb and at the dorsal tip of the bone. There are also other 20 ILLINOIS BIOLOGICAL MONOGRAPHS [190 sensory canals in the bone with openings at various points. The outer surface is smooth except that it has a narrow ridge at its postero-lateral edge which is located slightly anterior to the spines. The notch or pit formed by the curve is fiUed with a thin wavy sheet of bone which slightly overlaps the caudal edge of the shank of the hyomandibular. Slightly dorso-anterior to the ridge is a small roughened area for the articulation of the suborbital stay. Mandible. — The mandible is made up of three bones, the dent- ary, articular and the angular. A broad rounded ridge runs from slightly anterior to the head of the articular nearly to the anterior end of the dentary. On the inner surface of the dentary is a cavity within the bone corresponding to the ridge on the exterior; the articular has no cavity but a groove which corresponds to the ridge. In the bone beneath the ridge there is a latero-sensory canal which extends from the anterior end of the dentary to the posterior end of the articular. The dentary is a long bone with two long processes at the posterior end, forming a V-shaped angle which fits over the anterior process of the articular for its articulation with that bone. The lower surface is broadened by a mesial extension of a plate-like bone forming the ventral surface. Two kinds of teeth are present on the dentary, an inner row of the large canine ty^e and several irregular rows of the villiform variety. Articular. — The articular is united to the dentary by several bands where it fits into the V-shaped angle for the union of the two bones. This bone has a large facet for articulation with the quadrate. Here the bone is quite broad and gives off three processes. Slightly anterior to the facet it gives off a dorsal anterior process which unites with the dorsal process of the dentary by a cartilage. Immediately ventrad to this, and anterior to the facet, it gives off a long process, the anterior end of which fits into the V-shaped angle of the dentary. On the ventro-anterior edge it gives off the third process which fits over the ventral process of the dentary. There is a groove on the inner surface of the anterior and ventral processes and a deep pit on the antero-ventral edge of the facet. Ventro-posterior to the facet is located the angular bone which serves as an attachment for some of the mandibular muscles to the quadrate and also to the intraopercular. 191] OSTEOLOGY OF LORICATI—GUTBERLET 21 SCORPIONICHTHYS MARMORATUS The Cranium The skull (Figs. 2, 5) of Scorpionichthys differs from that of Ophidon only in a few points. The dorsal surface is somewhat more rounded and is covered with a granulated network. The temporal fossae are slightly different in shape and the orbits are smaller and more circular in outline, also the surface between them is narrower and concave. On the dorsal surface of the ethmoid the longitudinal groove, present in Ophidon, does not occur and a large erect process extending antero-laterally from the median line takes the place of the small ethmoid processes. There is a broad flange on the posterior end of the skull extending mesad from the caudal end of the epiotic ridge toward the median line, also the supra-occipital possesses a crest on the posterior surface extending from the dorsal edge to the end of the postero-ventral process. The anterior end of the temporal fossa is formed mainly by the edges of the granulated network of the parietals and pterotic. The parietal projects over the fossa for a distance as also does the epiotic which goes to make up a part of the mesial edge of the roof. Most of the roof is formed by the extra-scapular lying on the dorsal surfaces of the epiotic and pterotic across the fossa. In the dilatator fossa the sphenotic forms the greater part of the roof, in contrast to the condition in Ophidon; also there are no foramina in the fossa for the passage of the branches of the otic vessels. The vomer (Figs. 2, 5 v) is relatively smaller than in Ophidon but has the same general shape except that the lateral expansions are not as long and the dorsal process is shorter. Only villiform teeth are pres- ent; they are numerous and irregularly arranged. The dorso-anterior surface, slightly lateral to the median line, possesses a small articular facet for the articulation with a similar facet on the mesial edge of the maxilla. The ethmoid (Figs. 2, 5, eth) has no depression on its lateral sur- faces for the nasal pit. A tall antero-lateral process forms a V-shaped crest in the median line, supporting the nasal bones which roof the pit. The prefrontals (Figs. 2, 5, pfr) are relatively large, especially anteriorly; they lack depressions for the nasal pits. A thin flange extends ventro-caudad from the ventral surface of the lateral edge of the wing-like expansions to the mesial portion where it unites with the parasphenoid in the median line. On the lateral edge of the anterior portion, directly posterior to the vomer and anterior to the wing, there is a small facet for the articulation with the palatine. 22 ILLINOIS BIOLOGICAL MONOGRAPHS [192 The f rentals (Figs. 2, 5, fr) are somewhat shorter than in Ophidon and the surface between the orbits is markedly concave. The frontals unite with the sphenotics in the usual position and form a part of the orbit. The surface directly posterior to the orbit is somewhat depressed and forms a ridge on the ventral surface in the posterior part of the orbit. On the dorsal surface of the posterior portion of the bone there is a granulated network arranged more or less in longitudinal ridges with an irregular groove in the median line bounded by granulated ridges. The ventral surface is comparatively smooth and the part within the orbit is not porous as in Ophidon. There is a single ventral flange-like process on each side of the median line forming a part of the anterior boundary of the brain case. At the caudal end the flange is thickened and unites with the alisphenoid. A ridge extends from this point laterad to the edge of the bone at the place where it unites with the sphenotic, forming a triangular pit between the ridge and the ante- rior edge of the latter bone. There is also a small depression anterior to the ridge between it and the flange. In some specimens the flange comes in contact with the dorso-lateral process of the parasphenoid on the anterior edge of the alisphenoid. The ventro-posterior edge of the sphenotic (Figs. 2, 5, spo), in con- nection with the dorsal edge of the prootic dorsal to the arcade, forms a facet for the articulation with the anterior head of the hyomandibular. In Scorpionichthys the prootic forms nearly half of the facet while in Ophidon it forms only a very minor part of it. The sphenotic forms the greater part of the roof of the dilatator fossa, a condition slightly different from Ophidon where the pterotic forms the roof. The pterotic (Figs. 2, 5, pto) forms only a small part of the dilita- tor fossa and has a granulated surface. The alisphenoid (Fig. 5 als) is not porous and is not held between the two ventral processes of the frontal. It lacks a foramen for the passage of the cerebral veia such as Allis ( '09) found in Scorpaena and others. It forms the dorsal edge of a large foramen which is otherwise bounded by the edges of the prootic and the parasphenoid process. The basisphenoid and parasphenoid (Fig. 5, ps) are the same as in Ophidon except that in the parasphenoid there is a small partition between the two dorsal processes which separates the anterior and posterior portions. The prootic (Figs. 2, 5, pro) possesses a flattened process on its dorsal edge; this lies directly ventral to the hyomandibular facets and causes the hyomandibular to extend latereiUy from the skull. The ven- tral surface of this process contains a rounded pit which extends dorsad, almost between the hyomandibular facets. On the dorso-anterior edge, immediately dorsal to the arcade, the bone forms a part of the facet 193] OSTEOLOGY OF LORICATI—GUTBERLET 23 for the anterior head of the hyomandibular. In other respects this bone is like that of Ophidon except that the foramen for the external carotid artery, the jugular vein, and parts of the fifth and seventh nerves are located in a pit slightly mesial to the arcade. The epiotic (Figs. 2, 5, 7, epo) is flattened on the dorsal surface and extends caudad into a flattened process which forms a part of the dorsal surface of the cranium. On the meso-posterior edge a flange- like process from the posterior end of the bone extends meso-cephalad to the median line where it unites with a similar process on the supra- occipital. The lateral edges of the epiotics project slightly over the fossa and form a part of the roof. The parietals (Figs. 2, 5, p) have a granulated surface like that of the frontal and pterotic. They lie on the dorsal surface of the supra- occipital and form only a small part of the roof of the brain case at the edges of the supraoccipital. The bones do not meet their whole length in the median line, but leave the supraoccipital exposed. The supraoccipital (Figs. 2, 7, so) has a flange-like process on the posterior surface which is a continuation of that on the epiotic. The flanges of either side fuse in the median line where they come in con- tact with the crest which extends from the dorsal edge of the bone to the ventral edge of the process. Near the dorsal edge of the skull it forms a slight depression on the caudal surface in connection with the parietal. The basioccipital (Figs. 2, 5, 7, ho) and exoccipitals (Figs. 2, 5, 7, eo) are as in Ophidon, except that in Scorpionichthys the condylar pro- cesses and the basioccipital are longer. Facial Bones The maxilla is shorter and more flattened throughout its entire length than in Ophidon. On its ventro-mesial edge is a small facet for articulation with a similar facet on the dorsal surface of the vomer. The premaxillary (Fig. 10) is much shorter than in Ophidon but the dorsal processes are the same. Only villiform teeth are present which are numerous. The palatine is similar in all respects except that the mesial pro- cess is larger than in Ophidon, and only villiform teeth are present. The hyomandibular has a large flange-like process on the outer surface which extends ventro-posteriorly from the dorso-anterior angle formed by the irregular cross, to nearly the postero-ventral edge of the shank. The shank is broad and flattened throughout and unites with the preopercular, symplectic, and metapterygoid. The preopercular (Fig. 3) bears two spines, one long and pointed and the other short and somewhat rounded, a condition not found in 24 ILLINOIS BIOLOGICAL MONOGRAPHS [194 Ophidon. The dorsal edge of the bone is drawn out into a long slender process which lies on the posterior edge of the shank of the hyomandi- bular. The mandible is shorter than in Ophidon. There is no ridge on the lateral surface of the dentary nor is there a cavity within it ; also there is no mesial process on the ventral edge. It possesses villi form teeth but there seems to be a modification of the teeth in the inner row. These are longer than the others and have assumed more or less of a canine shape, placing the Scorpionichthys and Ophidon closer together. 195] OSTEOLOGY OF LORICATI—GUTBERLET 25 HEXAGRAMMOS DECAGRAMMUS The Skull The dorsal surface is smooth and more rounded than either Ophidon or Scorpionichthys, on account of the lateral extensions of the pterotic and prootic which makes a broad and flat rather than a deep temporal fossa. The supraoccipital is especially conspicuous as it separates the two parietals and comes to a spine-like point. On each side of the median line the parietals form narrow ridges which extend postero- laterally on the lateral edges of the epiotics and form the mesial edges of the roof of the temporal fossa. The dilatator fossae are shallow grooves in the sphenotic and pterotic bones. They lack foramina. The vomer (Figs. 12, 13) in this species has a relatively longer dorsal process than either Ophidon or Scorpionichthys. There is no articular facet on the dorso-anterior edge for the maxilla. Only villi- form teeth are present. The ethmoid (Figs. 12, 13) is not grooved but slightly keeled. It has no depressions for the nasal pits and the antero-lateral processes for the support of the nasal bone are similar to those of Ophidon. The prefrontals (Figs. 12, 13) have no depressions on the dorso- anterior edge for the nasal pits and have articular facets on the antero- lateral edges for the palatines as in Scorpionichthys. The frontals have a smooth dorsal surface which is slightly grooved between the orbits. It is not porous on the ventral surface and possesses a single flange process as in Scorpionichthys, differing from Ophidon and Scorpionichthys in not uniting with the sphenotic to form the pos- terior border of the orbit. As in Scorpionichthys, the sphenotic, in connection with the prootic, forms the facet for the anterior head of the hyomandibular. The pterotic is a thin flange-like bone extending postero-ventrally from the sphenotic, thus forming the ventro-lateral boundary of the temporal fossa. On the prootic there is a lateral flange-like process ventral to the facets for the hyomandibular; this extends out laterad below the facet for some distance, as in Scorpionichthys. The prootic forms a large part of the anterior facet for the hyomandibular. No special peculi- arities are shown in the arcade or the location of the foramina. 26 ILLINOIS BIOLOGICAL MONOGRAPHS [196 The parasphenoid has no partition between the lateral processes to separate the anterior and posterior portions and differs from Ophidon in that the ventral surface of the anterior portion bears a conspicuous ridge. The epiotic ends posteriorly in two processes. The condylar processes of the exoccipitals are relatively longer than in Ophidon but not as long as in Scorpionichthys. Facial Bones The premaxillary is relatively shorter than in Scorpionichthys and much shorter than in Ophidon. Villiform teeth are present but there is a modifification of these in the outer row, as they are much heavier and longer than those of the inner rows. The maxilla has a flange on its dorsal surface where it comes in contact with the first suborbital bone. Posterior to this flange the bone is flattened. There is a facet on the anterior mesial edge of the palatine where it comes in contact with the ethmoid. Only the villiform teeth are present. The shank of the^hyomandibular forms nearly a rectangular cross with the bar which bears the facets for the anterior head and the opercular bone. This causes the shank, which extends ventrally and slightly pos- teriorly in Ophidon, and directly ventral in Scorpionichthys, to extend antero-ventrally in this form. The metapterygoid has a short rounded anterior process and a groove, formed by lateral and mesial flanges, on the posterior edge for the shank of the hyomandibular and the hyoid artery. There are no particular differences shoAvn in the quadrate except that it is more anterior in this fish than in the other species described, a condition brought about by the position of the hyomandibular shank. The quadrate lies ventral to the anterior edge of the orbit while in Ophidon it lies ventral to the posterior edge and in Scorpionichthys it is ventral to the central portion of the orbit. The preopercular lacks barbs and spines and has no grooves nor ridges. It lies postero-ventral on account of the shank of the hyomandi- bular and the position of the quadrate. On this account the posterior end of the suborbital stay is somewhat lower. No lateral ridge is present on the mandible and no cavity within the dentary, nor is there a mesial flange on the ventral edge, as in Ophidon. The dentary is relativ^ely much shorter than in Ophidon and somewhat shorter than in Scorpionichthys. Villiform teeth are present but there is a slight modification of those of the outer row. They are longer and much heavier than those of the inner rows. 197] OSTEOLOGY OF LORICATI — GUTBERLET 27 SUMMAEY Since Ophidon and Hexagrammos belong to the same family, Hexagrammidae, one might expect something of a similarity in their osteology and also more marked differences between Scorpionichthys, belonging to the family Cottidae, and Ophidon. From a study of these forms I find that there are more differences between Ophidon and Hexagrammos than between Ophidon and Scorpionichthys. Some of the differences between Ophidon and Hexagrammos are, — 1. The dorsal surface is more rounded in the latter. 2. The supraoccipital possesses a conspicuous spine-like crest in the median line which entirely separate the parietals in Hexagrammos. 3. Foramina are present in the dilatator fossa in Ophidon but absent from Hexagrammos. 4. In Hexagrammos there are no nasal pit depressions on the eth- moid and prefrontal. The ethmoid is but slightly keeled and the anterior portion of the prefrontal possesses a lateral facet. 5. In Ophidon the frontal is thick and porous, but in Hexagram- mos, thin and smooth, with a single flange and a single groove on the ventral surface. 6. The sphenotic does not form part of the posterior edge of the orbit in Hexagrammos. 7. In Ophidon only a small part of the anterior hyomandibular facet is formed by the prootic, while in Hexagrammos this bone forms at least half of it. Also there is a conspicuous lateral prootic process below the hyomandibular facet in the latter genus. 8. In Ophidon the hyomandibular shank extends ventro-caudad while in Hexagrammos it extends ventro-cephalad, placing the quadrate further cephalad. 9. In Hexagrammos the preopercular spines and ridges found in Ophidon are absent, and the bone itself occupies a more ventral position. 10. Relatively, the mandible is twice as long in Ophidon as in Hex- agrammos and the dentary possesses no lateral ridge or cavity, nor a me- sial flange on the ventral surface. 11. A marked difference is found in the teeth in Ophidon and Hexagrammos. Both canine and villiform are found in the former but only the villiform in the latter. 28 ILLINOIS BIOLOGICAL MONOGRAPHS [198 Some of the likenesses between Ophidon and Scorpionichthys are, — 1. Dorsally, both skulls are flattened and have similar temporal fossae. 2. The sphenotic and the frontal bones form the posterior edge of the orbit, 3. The prootic arcade and the location of the formina are identical in both. 4. The alisphenoid and the parasphenoid are alike, with the exception of a small partition between the dorso-lateral processes of the para- sphenoid in Scorpionichthys- 5. Except for the longer premaxillary in Ophidon, the maxilla and the premaxillary are alike in both species. 6. The pterygoids, symplectic, and quadrate are alike in every respect. 7. In Ophidon, canine and villiform teeth are present and only villiform in Scorpionichthys, but in the latter the inner row of mandibu- lar teeth is better developed. 199] OSTEOLOGY OF LORICATI—GUTBERLET 29 BIBLIOGRAPHY Allen, Wm. F. 1905. The Blood Vascular System of the Loricati, the Mail-Cheeked Fishes. Proc. Wash. Acad. Sci., 7:27-157. Allis, E. p., Jr. 1889. The Anatomy and Development of the Lateral Line System in Amia calva. Jour. Morph., 2:463-568. 1897. The Morphology of the Petrosal Bone and the Sphenoidal Region of the Skull of Amia calva. Zool. Bull., i :i-26. 1897. Cranial Muscles and Cranial and First Spinal Nerves in Amia calva. Jour. Morph., 12:487-808. 1899. On certain Homologies of the Squamosal, Intercalar, Ex-occipitale, and Extrascapular Bones of Amia calva. Anat. Anz., 16:49-72. 1907. The Cranial Anatomy of the Mail-Cheeked Fishes. (Vorlaufige Mitt) Anat. Anz., 30:568-573. 1909. The Cranial Anatomy of the Mail-Cheeked Fishes. Zoologica, Hft. 57, 209 p. 8 pi. Gill, Theodore. 1888. On the Classification of the Mail-Cheeked Fishes. Proc. U. S. Nat Museum, 11:567-592. 191 1. Notes on the Structure and Habits of Wolf-fishes. Proc. U. S. Nat Museum, 39:157-187. Lucas, Frederic A. 1904. The Osteology and Immediate Relations of the Tile Fish, Lepholotilus chamaeleonticeps. Bull. U. S. Bur. Fish., 24:81-86, McMurrich, J. Playfair. 1884. The Osteology of Ameiurus catus. Proc. Can. Inst, 2:270-310. Parker, W. K. 1873. On the Structure and Development of the Skull in the Salmon. (Salmo salar L.). Bakerian Lecture II. Philos. Trans. Roy. Sec. London, 163 :95-i45. 1882. On the Development of the Skull in Lepidosteus osseus. Phil. Trans. Roy. Soc. London, 173 :443-492. Stark s, E. S. 1889. The Osteology and Relationship of the Percoidean Fish, Dinolestes Lewini. Proc. U. S. Nat Museum, 22:113-120. 1899. The Osteological Characters of the Fishes of the Suborder Percesoces. Proc. U. S. Nat Museum, 22:1-10. 1901. Synonymy of the Fish Skeleton. Proc. Wash. Acad. Sci., 3:507-539. 1908. The Characters of Atelaxis, a new^ Suborder of Fishes. Bull. Mus. Comp. Zool., 52:16-24. 1910. The Osteology and mutual Relationships of the Fishes belonging to the Family Scombridae. Jour Morph., 21 :77-ioo. Wright, Ramsay. 1885. On the Skull and Auditory Organ of the Siluroid Hypophthalmus. Trans. Roy, Soc. Canada (sec. 4), 3:107-118. 30 ILLINOIS BIOLOGICAL MONOGRAPHS [200 EXPLANATION OF PLATES Abbreviationj i als Alisphenoid pfo Postfrontal ho Basioccipital Pfr Prefrontal bs Basisphenoid pro Prootic eo Elx-occipital ps Parasphenoid epo Epiotic pto Pterotic eth Ethmoid so 'S'upra-ocdpital fr Frontal spo Sphenotic opo Opisthotic tf Temporal fossa P Parietal All figrures are reproduced from original drawings made bj' the author from preparations. 201] OSTEOLOGY OF LORICATI—GUTBERLET 31 PLATE I 32 ILLINOIS BIOLOGICAL MONOGRAPHS [202 EXPLANATION OF PLATE Fig. I. Dorsal view of skull of Ophidon elongatus. Natural size. .i:r<) BO EG PLATE I 203] OSTEOLOGY OF LORICATI—GUTBERLET 33 PLATE II 34 ILLINOIS BIOLOGICAL MONOGRAPHS [204 ' EXPLANATION OF PLATE Fig. 2. Dorsal view of skull of Scorpionichthys tnarmoratus. Natural size. PLATE II 205] OSTEOLOGY OF LORICATI—GUTBERLET 35 PLATE III 36 ILLINOIS BIOLOGICAL MONOGRAPHS [206 EXPLANATION OF PLATE I Fig. 3. Prepoercul^r of Scorpianichthys marmoratus. Two-thirds natural size. Fig. 4. Preopercular of Ophidon elongatus. Two-thirdds natural size. Fig. 5. Lateral view of skull of Scorpianichthys marmoratus. Two-thirds natural size. Fig. 6. Lattral view of skull of Ophidon elongatus. Two-thirds natural size. SPO AL'S BS PS V ETII OPO EO. fe"^^ spof^ppop PTp-rEPO rm PLATE III 207] OSTEOLOGY OF LORICATI—GUTBERLET 37 PLATE IV 28 ILLINOIS BIOLOGICAL MONOGRAPHS [208 EXPLANATION OF PLATE Fig. 7. Posterior view of skull of Scorpionichthys marmoratus. Three-fourths natural' size. Fig. 8. Posterior view of skull of Ophidon elongatus. Three-fourths natural size. Fig. 9. Premaxillary of Ophidon elongatus. Three-fourths natural size. Fig. 10. Premaxillary of Scorpionichthys marmoratus. Three-fourths natural size. PLATE IV 209] OSTEOLOGY OF LORICATI —GUTBERLET 39 PLATE V 40 ILLINOIS BIOLOGICAL MONOGRAPHS ' [210 EXPLANATION OF PLATE HEXAGRAMMOS DECAGRAMMUS Fig. II. Posterior view of skull. One and one-half times natural size. Fig. 12. Lateral view of skull. One and one-half times natural size. Fig. 13. Dorsal view of skull. One and one-half times natural size. PLATE V I .A'fiV e k rrw